The present invention relates generally to electronic article surveillance (EAS) systems and more particularly to a novel EAS marker for use in an EAS system and to a method of manufacturing said EAS marker.
The problem of protecting articles of merchandise and the like against theft has been the subject of numerous technical approaches. One such type of approach has been to attach to the article an electronic tag or marker that is adapted to trigger an alarm or the like if the article of merchandise is moved beyond a predetermined location and the electronic marker has not been deactivated or removed from the article of merchandise. In the aforementioned type of approach, a transmitting apparatus and a receiving apparatus are typically situated on opposite sides of a passageway leading to an exit of the premises being protected, the transmitting apparatus and the receiving apparatus together defining an interrogation zone. The transmitting apparatus is typically used to transmit over the interrogation zone an interrogation signal that is recognizable by the EAS marker and that causes the EAS marker, if activated, to emit a response signal. The receiving apparatus is typically used to detect the presence of a response signal from an activated EAS marker located within the interrogation zone. The detection by the receiving apparatus of a response signal indicates that the EAS marker has not been removed or deactivated and that the article bearing the marker may not have been paid for or properly checked out. Typically, the detection of such a response signal by the receiving apparatus triggers an alarm.
Several different types of EAS markers have been disclosed in the literature and are in use. In one type of EAS marker, the functional portion of the marker consists of either an antenna and diode or an antenna and capacitors forming a resonant circuit. When placed in an electromagnetic interrogation zone created by the transmitting apparatus, the antenna-diode marker generates harmonics of the interrogation frequency in a receiving antenna in the receiving apparatus; the resonant circuit marker causes an increase in absorption of the transmitted signal so as to reduce the signal in the receiving apparatus. The detection of the harmonic or signal level change indicates the presence of the marker in the interrogation zone. With this type of system, the marker is not amenable to deactivation and, therefore, must be removed from the article of merchandise at the time of purchase so as not to trigger the alarm when the merchandise is removed from the store.
Another type of EAS marker includes a magnetostrictive element, also referred to in the art as xe2x80x9ca resonator.xe2x80x9d Typically, the resonator is in the form of a ribbon-shaped length of an amorphous magnetostrictive ferromagnetic material. Said type of EAS marker also typically includes a biasing magnetic element. The resonator is fabricated such that it is mechanically resonant at a predetermined frequency when the biasing element has been magnetized to a certain level and the resonator is brought into an interrogation zone consisting of an AC magnetic field of the predetermined frequency. In use, the biasing element is activated, i.e., magnetized, and the marker is brought into the interrogation zone, thereby causing the resonator to mechanically resonate at the predetermined frequency. This resonant signal radiated by the resonator is then detected by circuitry provided in the receiving apparatus. By demagnetizing the biasing element, the bias is removed from the resonator; accordingly, when subjected to the AC magnetic field, the resonator no longer resonates to produce a detectable magnetic field. The marker can thus be activated and deactivated by magnetizing and demagnetizing the biasing element.
Examples of the aforementioned magnetomechanical type of EAS marker are disclosed in the following U.S. patents, all of which are incorporated herein by reference: U.S. Pat. No. 4,510,489, inventors Anderson, III et al., which issued Apr. 9, 1985; U.S. Pat. No. 4,510,490, inventors Anderson, III et al., which issued Apr. 9, 1985; U.S. Pat. No. 4,622,543, inventors Anderson, III et al., which issued Nov. 11, 1986; U.S. Pat. No. 5,351,033, inventors Liu et al., which issued Sep. 27, 1994; U.S. Pat. No. 5,469,140, inventors Liu et al., which issued Nov. 21, 1995; U.S. Pat. No. 5,495,230, inventor Lian, which issued Feb. 27, 1996; U.S. Pat. No. 5,568,125, inventor Liu, which issued Oct. 22, 1996; and U.S. Pat. No. 5,676,767, inventors Liu et al., which issued Oct. 14, 1997.
U.S. Pat. No. 4,510,489, which is illustrative of the aforementioned magnetomechanical type of EAS marker, discloses an elongated ductile strip of magnetostrictive, ferromagnetic material adapted, when armed, to resonate mechanically at a frequency within the range of an incident magnetic field. Suitable amorphous ferromagnetic metals, or metallic glasses, are disclosed for example in U.S. Pat. No. 4,553,136. Exemplary materials include the METGLAS alloys. Said strip is disposed adjacent to a ferromagnetic element, such as a biasing magnet capable of applying a dc field to the strip. The biasing magnet has a configuration and disposition adapted to provide the strip with a single pair of magnetic poles, each of the poles being at opposite extremes of the long dimension of the strip. The composite assembly is placed within the hollow recess of a rigid container composed of polymeric material such as polyethylene or the like, to protect the assembly against mechanical damping. The biasing magnet is typically a flat strip of high coercivity material such as SAE 1095 steel, Vicalloy, Remalloy or Arnokrome. Said biasing magnet is held in the assembly in a parallel, adjacent plane, such that the high coercivity material does not cause mechanical interference with the vibration of the strip. Generally, said biasing magnet acts as one surface of the package. Alternatively, two pieces of high magnetic coercivity material may be placed at either end of the strip, with their magnetic poles so arranged as to induce a single pole-pair therein. Alternatively, the bias field can be supplied by an external field coil pair disposed remotely from the marker in the exit passageway.
A magnetomechanical EAS marker that is integrated with an article of merchandise is disclosed in U.S. Pat. No. 5,499,015, inventors Winkler et al., which issued Mar. 12, 1996, and which is incorporated herein by reference. According to the aforementioned patent, the article of merchandise is provided with a structural member having an integrally formed cavity. A magnetostrictive element is housed within the cavity, the cavity being sized and shaped to house the magnetostrictive element without constraining the mechanical resonance of the magnetostrictive element. The cavity is closed by a sealing member affixed on the outer surface of the wall in a position such that the sealing member overlies the opening of the cavity. A biasing element is mounted on the outer surface of the sealing member, the biasing element being magnetically biased to cause the magnetostrictive element to be mechanically resonant when exposed to an alternating electromagnetic field generated at a selected frequency by the EAS system. According to an alternative embodiment, the biasing element may be formed as a layer of magnetic ink printed on the outer surface of the sealing member.
A self-biasing magnetostrictive element for a magnetomechanical EAS system is disclosed in U.S. Pat. No. 5,565,849, inventors Ho et al., which issued Oct. 15, 1996, and which is incorporated herein by reference. According to the aforementioned patent, the self-biasing magnetostrictive element is formed by first annealing a ribbon of ferromagnetic material in the presence of a magnetic field applied in a transverse direction relative to the longitudinal axis of the ribbon, and then annealing the ribbon a second time in the presence of a magnetic field applied in the direction of the longitudinal axis. The twice-annealed ribbon exhibits remanent magnetization along the longitudinal axis and has plural magnetic domains situated along the longitudinal axis. Said self-biasing magnetostrictive ferromagnetic element may be contained within a cavity of a plastic housing to form an EAS marker.
In U.S. Pat. No. 5,494,550, inventor Benge, which issued Feb. 27, 1996, and which is incorporated herein by reference, there is disclosed an EAS tag and a method of making the same. The method of the aforementioned patent comprises providing a continuous web of electrically insulative material, applying to opposed surfaces of the electrically insulative material web a succession of first and second electrically conductive coils and applying to the succession of first electrically conductive coils a normally electrically insulative deactivation structure extending across the first coil succession and convertible to be electrically conductive, the improvement comprising the step of providing an electrostatic charge drain in electrically conductive relation with each of the first electrically conductive coils substantially throughout the manufacture of the tags. The new step may be practiced by providing an electrically grounded, elongate, electrically conductive member across the succession of first electrically conductive coils in electrical continuity therewith.
In U.S. Pat. No. 5,357,240, inventors Sanford et al., which issued Oct. 18, 1994, and which is incorporated herein by reference, there is disclosed an EAS tag with a mechanically vibrating magnetic element and an improved housing and a method of making the same. The EAS tag of the aforementioned patent comprises a tag body having a central region, side wall regions connected to and integral with the central region and flap regions connected to and integral with the side wall regions. The tag body has fold lines at the junctions of the central and side wall regions and at the junctions of the side wall regions and the flap regions. By folding the tag body along these fold lines and, in the course of the folding procedure, inserting a first magnetic element, a substantially closed box-like housing with the first magnetic element loosely housed therein is formed.
Still another type of magnetomechanical EAS marker, which type is also one of the most widely used types of magnetomechanical EAS markers, comprises a plastic sheet material (e.g., styrene) which carries a heat seal coating. Said plastic sheet material is subjected to a thermoforming process to form a rectangular box-like housing with an open top bordered by a surrounding flange. A resonator is inserted into the housing through the open top, the resonator being curved slightly downwardly about its longitudinal axis. A clear, flexible, plastic sheet (e.g., polyethylene), often referred to as xe2x80x9clidstock,xe2x80x9d is placed over the top of the housing and is heat-sealed or laminated to the border flange so as to close the housing, thereby encasing the resonator therewithin. Due to the aforementioned process of laminating the lidstock to the housing, a downward curve or xe2x80x9cpillowxe2x80x9d is typically formed in the midsection of the lidstock, said pillow delimiting upward movement of the resonator within the housing. A double-sided adhesively-coated carrier sheet is laid down over the lidstock and is secured to the border flange of the housing. A biasing magnetic element is secured to the underside of the carrier sheet. A peelable liner is applied to the top surface of the carrier sheet. When using the marker, the liner is peeled from the carrier and the exposed adhesive surface thereof is pressed against a desired article of merchandise, thereby securing the article and the marker together. Typically, the marker is manufactured as part of a batch using a multi-stationed, turntable-containing apparatus analogous to that described in U.S. Pat. No. 5,357,240. A commercial embodiment of the aforementioned marker is sold by Sensormatic Electronics Corporation (Deerfield Beach, Fla.) under the xe2x80x9cUltraMaxxe2x80x9d trademark.
Although the aforementioned type of marker has been successful, the marker does possess some limitations. For example, as pointed out in U.S. Pat. No. 5,357,240, the flange of the housing, although needed for mounting the lidstock, increases the size of the housing, and for many applications, is aesthetically unattractive. Consequently, this prevents use of the marker with certain types of articles, and hence, in certain markets. In addition, the procedures carried out in fabricating the marker can result in the undesired bonding of the resonator between the lidstock and the marker housing. If this occurs, the required mechanical vibration of the resonator may be restricted and the resulting marker may not perform acceptably. Furthermore, the heat seal coating on the housing flange remains soft even after the marker manufacture has been completed. As a result, during shipment of the marker, the resonator may become attached to or lodged against the heat seal coating of the housing or may become stuck between the lidstock and the housing, thereby impeding the desired resonance of the resonator. Moreover, even if the resonator does not become lodged between the lidstock and the flange during manufacture or shipment of the marker, the mechanical vibrations of the resonator during use and/or the magnetic attraction between the resonator and the biasing element may cause the resonator to become lodged between the lidstock and the flange, thereby impairing performance.
Still another limitation of the aforementioned marker is that the marker is not highly resistant to being crushed by downward pressure applied from the top of the marker. Still yet another limitation associated with the aforementioned marker is that the above-described batch-wise technique for manufacturing the marker is not optimal in terms of throughput.
It is an object of the present invention to provide a novel EAS marker for use in an EAS system.
It is another object of the present invention to provide an EAS marker as described above that overcomes at least some of the shortcomings associated with existing EAS markers.
It is yet another object of the present invention to provide an EAS marker as described above that can be mass produced at a high rate of throughput.
According to one aspect of the present invention, there is described an EAS marker comprising a first trough-shaped member and a second trough-shaped member, said second trough-shaped member being joined to said first trough-shaped member to form a closed housing defining a cavity.
According to another aspect of the present invention, there is described an EAS marker comprising (a) a housing, said housing comprising a first piece and a second piece matingly secured to one another and defining a cavity therebetween, (b) a resonator disposed within said housing and (c) a biasing element disposed within said housing.
According to yet another aspect of the present invention, there is described an EAS marker comprising (a) a generally rectangular, closed housing made of a rigid material, said generally rectangular, closed housing having a cavity, (b) a resonator disposed within said cavity and (c) a biasing element disposed within said cavity.
According to still another aspect of the present invention, there is described an EAS marker comprising (a) a resonator container, said resonator container having a cavity and an open top, (b) a resonator disposed within said cavity of said resonator container, (c) a separator positioned over said open top of said resonator container, (d) a biasing element disposed on top of said separator for arming said resonator, and (e) a cover, said cover having a chamber and open bottom, said resonator container, said separator and said biasing element being disposed within said chamber and secured to said cover.
According to still yet another aspect of the present invention, there is described an EAS marker comprising (a) a housing, said housing having a cavity, (b) a resonator disposed within said cavity, (c) a biasing element disposed within said cavity for arming said resonator, and (d) a separator positioned within said cavity between said resonator and said biasing element for physically separating said resonator and said biasing element, said separator being made of a rigid material.
According to a further aspect of the present invention, there is described an EAS marker comprising a separator, said separator having a non-uniform cross-sectional thickness.
According to still a further aspect of the present invention, there is described an EAS marker comprising a separator made of a rigid material and being shaped to define at least one downwardly-extending projection.
According to still yet a further aspect of the present invention, there is described an EAS marker comprising (a) a housing, said housing comprising a top wall, said top wall having a recessed area and (b) a biasing element, said biasing element being positioned within said recessed area.
In a preferred embodiment, the EAS marker of the present invention comprises a top piece, the top piece being a generally rectangular, trough-shaped member having a top wall, a pair of side walls, a pair of end walls and an open bottom. Said top piece is made of a rigid, molded plastic, which may be polypropylene. The top wall of said top piece is provided with a recessed area, said recessed area having dimensions complementary to that of a biasing magnet of the type used in EAS markers.
Said EAS marker of the foregoing preferred embodiment also comprises a biasing magnet of the aforementioned type, said biasing magnet being disposed within said recessed area and being retained therein by a separator. Said separator, which is also made of a rigid, molded plastic, is a generally rectangular member having a flat top surface, a non-uniform cross-section thickness, and a bottom surface shaped to include a projection extending downwardly relative to the remainder of said bottom surface. The distance between the top surface of said separator and the bottom of said projection is approximately 0.010 inch. The top surface of said separator is press-fit against the interior surface of the top wall of said top piece.
Said EAS marker of the foregoing preferred embodiment further comprises a bottom piece, said bottom piece being a generally rectangular, trough-shaped member having a bottom wall, a pair of side walls, a pair of end walls and an open top. Said bottom piece is made of a rigid, molded plastic, which may be polypropylene. Said bottom piece is press-fit within said top piece and against said separator, with the side walls and end walls of bottom piece engaging the corresponding side walls and end walls of said bottom piece. In this manner, said separator and said bottom piece together define a resonator cavity.
Said EAS marker of the foregoing preferred embodiment additionally comprises a resonator, said resonator being loosely encased within the resonator cavity and being bowed slightly downwardly about its longitudinal axis. Said resonator has a non-vibration node of approximately 0.1 inch located at or about its midportion. Said projection of said separator is aligned with said non-vibration node and is dimensioned to contact said resonator only within said non-vibration node.
According to still yet another aspect of the present invention, there is described a method of manufacturing a container for use in an EAS marker, said method comprising the step of continuously molding a web of plastic material, said web being shaped to include at least one container adapted to hold an EAS component.
According to even still yet another aspect of the present invention, there is described a method of manufacturing an EAS marker, said method comprising the steps of (a) continuously molding a container, said container having a cavity and an opening for permitting access to said cavity, and (b) inserting through said opening and into said cavity of said continuously molded container means for emitting a response signal in response to an interrogation signal transmitted by an EAS system.
According to still a further aspect of the present invention, there is described a method of manufacturing a magnetostrictive EAS marker, said method comprising the steps of (a) providing a resonator container, said resonator container having a resonator cavity and an open top, (b) inserting a resonator into said resonator cavity through said open top, (c) providing a biasing element container, said biasing element container having a biasing element cavity and an open bottom, (d) inverting said biasing element container, (e) inserting a biasing element into said biasing element cavity of said inverted biasing element container, (f) encasing said biasing element within said biasing element container with a separator, (g) inverting said biasing element container to its original orientation, and (h) joining said resonator container and said biasing element container to form a magnetostrictive EAS marker comprising a resonator and a biasing element wherein said resonator and said biasing element are separated by said separator.
According to still yet a further aspect of the present invention, there is described a method of manufacturing a magnetostrictive EAS marker, said method comprising the steps of (a) continuously molding a first web, said first web comprising a plurality of resonator containers, each of said resonator containers having a resonator cavity and an open top, (b) inserting a resonator into through the open top and into the resonator cavity of a first resonator container on said first web, whereby a first marker subassembly is formed, (c) continuously molding a second web, said second web comprising a plurality of biasing element containers, each of said biasing element containers having a biasing element cavity and an open bottom, (d) inverting said second web, (e) inserting a biasing element into the biasing element cavity of a first biasing element container on said inverted second web, (f) continuously molding a third web, said third web comprising a plurality of separator elements, (g) joining a separator element on said third web to a biasing element container on said second web in such a way as to encase said biasing element within said biasing element container, whereby a second marker subassembly is formed, and (h) joining said first marker subassembly to said second marker subassembly to form a magnetostrictive EAS marker comprising a resonator and a biasing element wherein said resonator and said biasing element are separated by said separator element.
According to even still yet a further aspect of the present invention, there is described a method of forming a laminate structure, said method comprising the steps of (a) providing a first web, said first web comprising a plurality of first elements, (b) providing a second web, said second web comprising a plurality of second elements, said second elements being alignable with said plurality of first elements, and (c) passing said first web and said second web through a lamination nip to join said first elements and second elements.
One aspect of the invention relates to the creation of multiple xe2x80x9cmaster rollsxe2x80x9d of components of an electronic article surveillance device, or marker; and the assembly of these components through roll lamination techniques. Each of the xe2x80x9cmaster rollsxe2x80x9d consists of a web of plastic material, which carries a series of components of the device to be assembled. The web may be continuous or discontinuous.
The components can be periodically or aperiodically spaced on the web, and the components mounted in a given master roll can be the same as each other, or different from each other. In a preferred embodiment, the components are formed in an orthogonal matrix with multiple components arrayed across the width of the web. Preferably, in a given master roll, the components are formed or molded of the same material as the web, but it is also possible to mount or insert components into the web comprising a different material than that used to form the web. In effect, the web serves as a carrier for the components.
A wide variety of molding or forming techniques can be used to create the master rolls of plastic material. Exemplary techniques include continuous molding, injection molding, and thermoforming. Thermoforming is commonly used to form sheets of plastic material into trays, tubs, and the like. The sheet is heated to the proper forming temperature; then, a vacuum draws the sheet down directly onto a male mold or into a female mold. Pressing the sheet between male and female molds is another thermoforming technique.
Preferably, the process for forming the master rolls is continuous molding. A variety of continuous molding processes are known for continuously extruding molten plastic into a molding member. The molding of a master roll as described above is particularly well suited to continuous molding. The type of continuous molding used in a preferred embodiment utilizes a cooled molding wheel.
The manufacturing process of the present invention combines multiple components through lamination at a lamination nip (or at a series of nips). Typically, but not necessarily, the nip is defined by two rollersxe2x80x94roll lamination. Components may be combined at the nip using a variety of techniques, including e.g. press fitting, adhesive lamination, heat bonding and the like. As used in the present specification and claims, xe2x80x9claminationxe2x80x9d and xe2x80x9claminatexe2x80x9d encompass any of the wide variety of such techniques, and these terms are not limited to particular techniques such as adhesive lamination.
Roll lamination is an efficient and flexible process which may be combined with other assembly processes for in-line production of EAS markers of the present invention. This combination of roll lamination with other assembly processes is exemplified by the manufacturing process detailed below.
Additional objects, features, aspects and advantages of the present invention will be set forth, in part, in the description which follows and, in part, will be obvious from the description or may be learned by practice of the invention. In the description, reference is made to the accompanying drawings which form a part thereof and in which is shown by way of illustration specific embodiments for practicing the invention. These embodiments will be described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural changes may be made without departing from the scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is best defined by the appended claims.